http://www.realsentrygun.com/engine.mp3

This is in a ford ranger 1999 2.5L 120,000mi. There are two different knocks, a constant low knock and a much louder, intermittent but mostly present tapping. Removing the spark from each cylinder has no obvious effect. It still has the same power and runs smooth. Oil pressure is fine. Temp is fine. No smoke.

Going down the list of possibilities tell me if any of my conclusions or tests are wrong:

1. "A rod knock intensifies with load or acceleration. A bad rod bearing will make more noise under stress of combustion." Can't be this since it's there at all rpms, warm or cold, stress or no stress.

2. "Car in drive while running, lightly hit throttle, if "knocking" goes away after hitting gas WHILE holding brake your cause is flex-plate and not engine-related." Can't be the flex plate since it doesn't go away during this test.

3. "If it gets louder under load, it's probably an exhaust leak." It doesn't. It stays the same.

4. "If it stays constant, then a lifter or other valve train noise." This is a possibility but it's SOHC and I found nothing loose when pulling the valve cover..

5. "Piston slap sounds kinda like dominoes falling and lessens upon warm up, but doesn't go away and sounds like a diesel while driving under low rpm. Piston slap will go away when plug wire is pulled." pulling the plug wire for each cylinder has no effect on the tapping.

6. "*Out of tune valves sounds like a light tapping while the motor is idling, followed by deteriorated higher rpm performance" No deteriorated higher rpm performance.

7. "Bent valves sound like some LOUD *** tapping under all rpm ranges. zero compression is a sure tell sign of a bent valve" It is loud but seems to run fine. I should do a compression test anyway.

8. "*Spun bearing sounds like someone threw a wrench in your oil pan." Noise isn't loud in the oil pan. It's loud using a stethoscope on the valve cover, intake and exhaust manifolds.

What do you think it is?

 

That is definately a rod !!!!
Not sure about the intermittent one though.

 

What are you using to check the oil pressure?

 

The dash gauge :/